1. Field of the Invention
The present invention is related to conditional access devices. In particular, the present invention is related to interfacing a conditional access device to a digital device.
2. Description of Related Art
Modern set-top boxes generally have a receiver to receive program data, or content, from a service provider and generate multiple transport streams. The content is normally scrambled before being transmitted to the receiver. The scrambled content is then de-scrambled by a conditional access (CA) device. Currently, entitlement management messages (EMM) typically use unique keys or signatures to deliver a group key or access parameters to CA devices. An EMM is a message used to deliver privileges (e.g., rights, keys) to a CA device. Typically the group are users or customers who share a particular set of entitlements. The National Renewable Security System (NRSS) defines two types of CA devices or modules: an NRSS part A module supporting a smart card form factor, and an NRSS part B module supporting a PCMCIA form factor.
The unscrambled content is then transferred or downloaded to a digital device such as a display device (e.g., digital television) for program viewing or a recording device (e.g., digital video cassette recorder) for program recording. In many scenarios, multiple digital devices are connected to the conditional access device for simultaneous activities such as viewing while recording or viewing at different display locations.
A standardized interface between the conditional access device and the digital device is desirable. However, it is important to safeguard the content or transport streams from unauthorized copying by the digital device. In addition, the interface should be flexible enough to accommodate several usage options such as store and playback.
Therefore, there is a need to have an efficient and flexible technique to interface a conditional access device to a digital device.